Re: [RFC][PATCH 12/12] PM / r8169: Add simplified run-time PM support

Rafael J. Wysocki
2010-01-04T19:51:08Z

On Monday 04 January 2010, Pavel Machek wrote:
>
> > > > Using /proc/acpi/battery/BAT1/state I measured the energy drawn in 10 minutes
> > > > both with the network adapter in D0 and D3hot. The results were that with the
> > > > network adapter in D0 the box drew 2476 mWh, while with the network adapter in
> > > > D3hot it drew 2361 mWh. The difference is 115 mWh, or about 5% on this
> > > > particular box.
> > > >
> > > > This means about 0.1 Wh in 10 minutes, so we can save about 0.6 Wh per hour.
> > >
> > > Which means it saves 0.6W :-). Measuring power in Wh/h is "interesting".
> >
> > You can't save power, you can only save energy. Wh is just an energy unit.
>
> Of course we can save power, you just did :-).
>
> (And in some cases -- data centers, limited cooling -- you are limited
> by power, not energy.

But still energy is what you pay for, isn't it?

> You are right that on notebooks, energy is more important.)

You may require less power to run, so if that's what you mean by "saving", then
I agree. :-)

Rafael